The present invention relates to the structure of a motor and particularly, to a motor for use in a magnetic disk unit to rotate the magnetic disks at high speed, the mounting structure thereof, and the controlling method thereof.
As disclosed in Japanese Laid-Open Pat. No. 62-212968 or in HITACHI Review Vol. 37 (1988), No. 5 p. 283 -p.290, the conventional magnetic disk unit is so constructed that a motor is directly mounted at an end of the shaft to which a magnetic disk is fixed and is driven to rotate it. This motor is of an outer-rotor type having a cup-shaped rotor, and the rotor is positioned so that its opening faces the side of the chamber (enclosure) where the disk is stored. In the portion covered by the rotor, a stator is installed, and the stator is fixed to the non-rotatable portion of the motor. A board having the hall element to detect the position of the rotor is provided on the non-rotatable portion of the motor.
Furthermore, as described in Japanese Utility Model Publication No.51-49934, a magnetic shielding board is provided between the motor and the magnetic disk in order to protect the magnetic disk from any effect caused by a leakage of the magnetic field from the motor.